1. Technical Field of the Invention
The present invention relates to mechanical interface apparatus provided in various types of processing apparatus for processing semiconductor wafers, for loading semiconductor wafers stored in sealed containers into the processing apparatus without exposing them to air.
2. Background Art
Conventionally, semiconductor devices are manufactured inside clean rooms which have cleansed interior atmospheres. Moreover, in order to prevent the adherence of the slightest amounts of dust in these clean rooms, the semiconductor wafers are often transported during the manufacturing process while stored inside wafer cassettes, which are themselves stored inside transportable sealed containers.
When the semiconductor wafers are stored inside these sealed containers, the sealed containers are filled with inert gases such as nitrogen in order to replace their interior atmospheres with inert gas, so as to prevent the formation of natural oxidation films or organic contaminants on the surfaces of the semiconductor wafers due to water vapor, oxygen, and other gases which may be present in the container atmosphere.
FIG. 22 shows the outward appearance of a sealed container as mentioned above, and FIG. 23 shows a cross-sectional view. In FIGS. 22 and 23, reference numeral 10 denotes a container body of a sealed container 100, having a flange 103 formed on a mouth portion 102. Reference numeral 104 denotes a handle 104 which is gripped by a human hand or a manipulator provided on a transport cart when the sealed container is being transported. Reference numeral 105 denotes a sealing material attached to the peripheral portion of a bottom lid, for keeping the sealed container airtight. Reference numeral 106 denotes a wafer cassette loaded with a plurality of semiconductor wafers, which is placed on the top surface of the bottom lid 110 when stored inside the sealed container 100.
The bottom lid 110 is hollow, and the interior is provided with a lock mechanism as shown in FIGS. 24 and 25. While FIG. 23 only shows the structure of the left half of the sealed container, the right half has an identical structure to the left half.
In FIG. 24, reference numeral 111 denotes a lock arm having a flattened rod shape. As shown in FIG. 25, the lock arm 111 has a rolling element 111a on one end, through which it is attached to a cam 112 so as to be capable of tilting and moving in a longitudinal direction. The other end of the lock arm 111 is fitted into a concave portion 103 formed on the inner circumferential surface of the flange 103 of the container body 102 when locked, thereby affixing the bottom lid 110 to the container body 101. Reference numeral 113 denotes support members which support the lock arm 111 near the center of the lock arm 111 in the longitudinal direction. Reference numeral 114 denotes a spring for biasing the lock arm 111 downward as shown in FIG. 24.
Reference numeral 120 denotes a lock operating mechanism provided with a gas purge unit for refilling the sealed container with inert gas, and various types of processing apparatus for processing semiconductor wafers, the interior of which has a cam shaft 121 the tip of which is in spline engagement with the cam 112 on the bottom lid 110, and a drive mechanism 122 for rotating the cam shaft 121. The lock operating mechanism 120 is capable of being moved up and down as seen in FIG. 24 by means of an elevator mechanism not shown in the drawings. When the sealed container is to be opened or closed, the lock operating mechanism 120 is raised into contact with the bottom lid 110 in order to lock or unlock the lock mechanism provided in the bottom lid 110.
That is, in the case of unlocking, the drive mechanism 122 rotates the cam shaft 121 which is in spline engagement with the cam 112 counterclockwise by a predetermined angle so as to withdraw the other end of the lock arm 111 from the concave portion 103a. In the case of locking, the other end of the lock arm 111 is inserted into the concave portion 103a by rotating the cam shaft 121 clockwise by a predetermined angle. Then, upon locking, the bottom lid 110 is brought into tight contact with and affixed to the container body 101 with the sealing material 105 pinched therebetween, so as to maintain the interior of the container so as to be airtight.
Conventionally, the various semiconductor wafer processing apparatus for processing semiconductor wafers in various ways (such as cleansing, surface treatment or film formation) have SMIF (standardized mechanical interface) systems for placing semiconductor wafers stored in sealed containers in such apparatus without contamination by particles from the external atmosphere. With reference to FIGS. 26 through 29, the operations involved in placing semiconductor wafers in sealed containers within the apparatus by means of an SMIF system will be explained.
Before explaining the operations, the structure of the SMIF system of the processing apparatus 200 will be explained with reference to FIGS. 26 through 29. In this case, the sealed container of FIGS. 26 through 29 is identical to the sealed container explained with reference to FIGS. 22 through 25, so the explanation will be omitted.
In FIG. 26, reference numeral 200 denotes a processing apparatus for performing a predetermined process on semiconductor wafers. The atmosphere within the apparatus is cleansed. Reference numeral 201 denotes latch mechanisms which move in the directions of the arrows E when a sealed container 100 is placed thereon, so as to engage with the flanges 103 and affix the container body 101 to the processing apparatus 200.
Reference numeral 202 denotes an in-apparatus elevator mechanism, attached with a lock operating mechanism 220, which moves up and down along a rail 203. In this case, the lock operating mechanism 220, like the lock operating mechanism 120 shown in FIG. 24, has a cam shaft 221 and a drive mechanism (not shown in the drawings), and locks and unlocks the bottom lid 110, but the main body of the lock operating mechanism 220 is provided with a flange 223. When the in-apparatus elevator mechanism 202 is at the highest position (the position of the in-apparatus elevator mechanism 202 as shown in FIGS. 26 and 27), the interior of the apparatus is made airtight due to the upper surface of the flange 223 coming into tight contact with the inner surface 205 at the periphery of the open portion 204 of the processing apparatus 200, thereby keeping the internal atmosphere clean.
The operations of the above-mentioned processing apparatus 200 will be explained next. First, as shown in FIG. 26, when a sealed container 100 is placed on the processing apparatus 200 by means of a manipulator, a cam (not shown in the drawing) in the bottom lid 110 of the sealed container comes into spline engagement with the cam shaft 221. When this is sensed by a sensor which is not shown in the drawings, the latch mechanisms 201 move in the directions of the arrows E so as to engage with the flanges 103, thereby affixing the container body 101 to the processing apparatus 200.
Next, as shown in FIG. 27, the drive mechanism (not shown in the drawings) in the lock operating mechanism 220 is activated so as to rotate the cam shaft 221 by a predetermined angle, and withdraw the other end of the lock arm 111 from the concave portion 103a. This unlocks the bottom lid 110, after which the in-apparatus elevator mechanism 202 is lowered to a predetermined position with the bottom lid 110 carrying the wafer cassettes 106 still placed on the top surface of the lock operating mechanism 220, as shown in FIG. 28. Then, the wafer cassettes 106 are loaded into the processing apparatus 200 by means of cassette loading mechanisms or the like (not shown in the drawing) which are provided inside the apparatus, as shown in FIG. 29.
In this manner, a processing apparatus having an SMIF system allows semiconductor wafers to be removed from sealed containers without being exposed to the external air, thereby keeping the semiconductor wafers from being contaminated with dust or the like which can exist in the external air.
As shown in FIG. 30, the above-mentioned SMIF system is such that there is a possibility of dust from the clean room adhering to the bottom surface A of the bottom lid 110, and the gap B formed by the outer circumferential surface of the bottom lid 110 and the inner circumferential surface of the flange 103, which are exposed to the external air when the sealed container 100 is moved. Additionally, on the side of the processing apparatus 200, there is a possibility of dust adhering to the top surface C or the lock operating mechanism 220, and the gap formed by the outer circumferential surface 220a of the lock operating mechanism 220 and the inner circumferential surface 204a of the opened portion of the processing device 200 when the sealed container 100 is not in place.
Furthermore, since the bottom lid 110 has a hollow structure as mentioned previously, there is the risk of dust penetrating into the bottom lid 110 through the slight gap formed between the lock arm 111 and the hole for allowing the other end of the lock arm 111 to pass through from the interior of the bottom lid 110.
When dust has adhered to the gap B or the gap D, or when dust has penetrated inside the bottom lid 110, there is a risk of the dust penetrating into the processing apparatus and adhering to the semiconductor wafer when the semiconductor wafers are loaded into the processing apparatus. Additionally, the bottom surface A of the bottom lid 110 and the top surface C of the lock operating mechanism 220 are brought into contact when the sealed container 100 is placed on the lock operating mechanism 220, but gaps may form depending on the work precision of the surfaces, so that dust sticking therein may penetrate into the processing apparatus 20.
Furthermore, external air penetrates into the bottom lid 110 when the sealed container 100 is being transported, and the spaces formed in the gaps B and D are filled with external air when the sealed container 100 is placed on the processing apparatus 200, so that when the sealed container 100 is filled with an inert gas such as N.sub.2 gas, the external air existing in the spaces can contact the semiconductor wafers during the unlocking of the lock mechanism for loading the semiconductor wafers 106 into the processing apparatus 200, which may adversely affect the wafer surfaces.